This invention relates to a multiband radio receiver with an electronic preset tuning system, and more particularly to a multiband radio receiver in which a station to be received can be preset accurately.
Recently, due to the rapid progress of electronic engineering, a variety of radio receivers, in which a band and a channel of a station to be received can be preset, have been proposed. For example, a digitally controlled preset radio receiver was disclosed in applicant's Japanese Utility Model Application No. 11353/1975. In the above conventional radio receiver, the channel preset system comprises a preset switch; a channel selecting switch; a pulse generator for selectively generating up pulses and down pulses; an UP/DOWN counter connected to the pulse generator; a digital display means for displaying a frequency value in response to the digital output signal of the U/D counter; a digital-to-analog convertor connected to the U/D counter to convert the digital output signal thereof into an analog signal, the analog signal being applied to variable capacitance diodes (varactor diodes) in a tuning circuit; a memory means such as a random access memory (RAM) for memorizing the output of the U/D counter and providing outputs as to the data addressed therein to the U/D counter; and a control circuit for controlling write and read-out operation of the RAM. The channel selecting switches described above are, for instance, non-lock type selecting switches, while the band selecting switch is a rotary switch. Whenever a channel selecting signal outputted by each channel selecting switch and a band selecting signal outputted by the band selecting switch are detected, the output of the memory is inputted into the U/D counter so as to carry out the necessary control operation.
In this case, however, the radio receiver as described above is disadvantageous in the following points; that is, since an automatic frequency control (AFC) circuit is operated during the preset operation of a station being received, it is impossible to determine whether a preset frequency value is accurately tuned in. Accordingly, there is a possibility that an inaccurate frequency value is preset. As a result, in the case when preset station selection is carried out in accordance with the preset frequency value, it may be impossible to accurately achieve the preset station selection.